In current practice, High Definition (HD) programming content is delivered to consumers via video equipment such as DVD players, set top boxes (STBs), etc. in a compressed digital form that is produced by the content creator. The video equipment decompresses the media (video and audio) streams in order to display the video on the television (TV) screen. Program creators typically use expensive and high-quality compression equipment to ensure excellent picture quality and reasonable program bandwidths.
In order for the user to select preferences or control the video equipment, the video decoding product then, when appropriate, blends a graphics overlay or OSD stream containing menus, information, status, etc onto the program. The combined signal is then sent to the TV display using either an analog or digital signal in a form that is not compressed.
An OSD is an image that is presented along with one or more other images from a different source on a screen. The OSD may or may not be transparent such that the OSD and another image can be simultaneously seen. The OSD may be purely informational (such as an OSD indicating the current channel of a TV or a stock ticker) or a graphical user interface (GUI) that allows a user to select a feature through, for example, a remote control device. The OSD is often generated from a different source and is superimposed on another image such that a portion of the other image is partially or completely not displayed while the OSD is displayed. For example, a TV, DVD player, STB, or other device can generate information such as volume, channel, time information, or a menu in response to signals from a remote control device or the pressing of buttons on the TV, set top box, DVD player, or other video source device. In addition to being used in TVs, OSDs have also been used in connection with computer displays. Some video equipment boxes may include more than one video source device. Some video devices are both video source devices and video display devices.
The OSD signals can be generated inside control circuitry of the TV or inside other devices such as a set top box or DVD player and be provided remotely from these devices to the TV. For example, when a remote control device provides a channel change command to a TV, control circuitry in the TV may cause an OSD with the new channel to appear on the TV screen. Alternatively, if the remote control device provides a channel change command to a set top box, the set top box may generate OSD signals and provide the OSD signals to the TV to be displayed on the TV screen.
Referring to FIG. 1, a prior art system includes a video signal source 12 which provides compressed or uncompressed video to a set top box 16. Examples of the video source include a cable TV outlet and a satellite TV receiver. Examples of set top boxes include cable TV boxes and satellite TV boxes. Source 12 also provides audio signals, which will not be further discussed. Set top box 16 provides uncompressed analog video signals or uncompressed digital video signals to a display control circuitry 20 of a TV 18. As an example, uncompressed digital video signals may be provided between set top box 16 and display control circuitry 20 of TV 18 through a High Definition Multimedia Interface (HDMI). Display control circuitry 20 could receive video from other devices including a DVD (Digital Versatile Disc) player, DVR (digital video recorder), VCR (video cassette recording device), hand held video source device, or other device, in addition to or in replace of set top box 16.
The video signals are provided from display control circuitry 20 to display 30 to be displayed on screen 34. In the case in which OSDs are generated by set top box 16, the OSDs may be combined as part of the uncompressed video signals and sent to TV 18 to be displayed. Display control circuitry 20 includes a frame buffer 24 to present OSD signals that are combined with the uncompressed video in blender circuitry 26. Blender circuitry 26 provides the combined signals to display 30 to be displayed on screen 34.
Various attempts have been made to provide TV signals over home entertainment networks. A naïve approach to extending the system of FIG. 1 for use over a network (which does not have enough bandwidth to carry the raw video signal) would be to recompress the combined video and OSD information before transmission. However, compression equipment that would be affordable to include in a home video product would produce a noticeably degraded picture quality compared to the originally compressed program. Since a main motivation for a consumer to purchase a HD TV is to obtain improved picture quality and resolution, this would not be an acceptable result.